In places that require variable illumination, such as homes, theaters, auditoriums, and the interiors of automobiles, it is desirable to gradually change the level of illumination in order for the human eye to comfortably adapt to changes in light intensity. Such a change in illumination is achievable via electronic and computer control, from computer controlled interior lighting systems to simple light dimmer circuits.
As the requirements for lighting systems have become more sophisticated, however, the circuitry required to support time variable lighting control has required high system and circuit complexity, precise analog components, and high resource demands both in terms of circuit board area and the number of required electronic components. The interior of an automobile, for example, may require at least a dozen lights, each of which are independently controllable. While a microcontroller can be used to generate independent pulse modulated signals to vary the intensity of each light, the disadvantage of such an approach is that microcontrollers typically have a limited number of available hardware resources such as timers, interrupt lines, and general purpose I/O pins. The use of software and CPU resources to track and control dimming profiles of multiple lights leaves fewer resources available to other automotive applications such as power train and safety systems.
In the field of illumination systems, what are needed are cost effective systems for the control of light intensity.